Smart grids accept distributed intermittent generations (renewables) such as wind, photovoltaic, high energy batteries to enhance overall power system operations. The key challenges to interconnect such generations into the grid are: (1) advanced regulatory mechanisms are needed to maintain high energy efficiency, power quality and reliability during their fluctuations, (2) backup storage due to its intermittent nature. Distributed energy storage systems (capturing, storing and releasing electric power in large amount) help smart grid to optimize utilization of distributed generations. Storage systems are also of great importance, not just for integrating renewable energy sources, but for the variations in the demand. Several possible technologies for electricity storage are including high energy batteries, flywheels, superconducting magnetics, compressed air, and pumped hydroelectric. Among the mentioned technologies, pumped hydro is a reliable and bulk storage system.
Pumped Storage Plant (PSP) has gained a high level of attention in recent years, mainly because of its ability to act as a large-scale energy storage option and to improve power system flexibility. The total installed capacity of fixed speed PSP in India is 4804 MW out of worldwide capacity of 130 GW. The fixed speed PSP suffers from limited deviation in water head and inability to operate in partial pumping mode. These drawbacks can be overcome by the transformation of PSP from fixed speed mode to variable speed mode. Variable speed PSP employing Doubly Fed Asynchronous Machine (DFAM) is emerging now in hydropower applications. In India, the first variable speed PSP having 4 nos. of 250MW DFAM totaling to a capacity of 1000 MW is under construction at the Tehri Dam of Uttarakhand state.
The theme of NWPE 2017 is “Strengthening Grid Energy Storage through Power Electronics-Challenges and Research Opportunities”.
Power electronic converters play a major role in these plants by facilitating real and reactive power control and part load operation (i.e. variable speed). In fixed speed hydropower plants, thyristor-based power electronic converters are used in the excitation system (DC) having a lower power rating in comparison with machine rating. On the other hand, the rating of excitation system (AC) equipped with power electronic converter is quite large in DFAM fed variable speed PSP which handles slip power of the machine (Ex: For a typical 250MW doubly fed induction machine with the target of ±10% speed variation, power converters need to handle 25MW (slip power) of power with the current rating of 12,000 A). Due to the requirement of large power rating there is a critical necessary to opt for the multichannel (parallel) converters in DFAM fed variable speed PSP.
The application of semiconductor devices in PSP ranges from silicon based naturally commutated devices (Thyristor) to self-commutated devices (IGBT, IEGT, IGCT, etc.,) depending on the requirements such as switching characteristics, ease of gate control, reliability, low on state power losses and voltage drop, etc. In a similar way, the advancement in power converter topology ranges from cycloconverter to multi-level voltage source converters to achieve harmonic distortion reduction, pure sinusoidal supply, etc. There are more operational challenges in multichannel parallel power converters in these plants as it needs to be stopped for few hours in case of a typical fault occurred in power electronics converters.
NWPE 2017 (The National Workshop on Power Electronics) is proposed for three days to offer a unique opportunity to the experts from major industries, academic institutions, distinguished practitioners in power electronics technology and graduate engineers to exchange their experiences, new ideas, practical challenges encountered and the possible solutions towards the theme of the workshop Strengthening Grid Energy Storage Through Power Electronics -Challenges and Research Opportunities. Lectures/presentations in the workshop will be by invited speakers from hydropower development corporations, power electronic manufacturing industries, R&D organizations, educational institutions in India and in abroad. Two sessions for industry interaction will be organized on the third day to receive feedbacks on industry requirements in the area of power electronics.
The main objective of NWPE 2017 is to explore the operational challenges and research opportunities in grid level energy storage systems to integrate renewable energy sources. This can be described in a series of following sub-objectives.
1. Bring together senior professionals in the field of power electronics to provide helpful information to younger professionals.
2. Explore the current trends in power electronics used for solar and wind power systems.
3. Explore the challenges and opportunities in grid level energy storage systems.
4. Emphasize active power sharing and circulating current reduction techniques in multichannel power converters fed variable speed pumped storage plants (PSP).
5. Explore power and control redundancy issues with the power converters used in PSP.
6. Explore the Control complexity of Multichannel Power Converters in the presence of Phase Shift Transformers.
7. Explore advanced protection techniques for large rated power electronics converters.
8. Explore the research opportunities in power electronic converters for grid energy storage in view of the following:
** WBG devices
** Converter topology
** Power sharing
** Coordinate control system
** Soft
isolation of converter during faults
** Compensation for changing energy output from wind and solar
